在C ++中从短到字节签名 [英] signed short to byte in c++

问题描述

我正在尝试使用C ++
将十六进制数转换为短整数（2字节），除一件事情外，其他都没问题...从短符号转换为字节（最后一次测试）

I'm trying to convert a HEX number into a short (2 Bytes) using C++ everything is OK except for one thing... signed conversion from short to Byte (last test)

我发现了这个问题，不能真正从中受益：便携式有符号/无符号字节转换，C ++

i found this question and couldn't really benefit from it: portable signed/unsigned byte cast,C++

这是我的测试：

// test 1 - positive B2Short (success)
byte *b = new byte[2];
b[0] = 0x10; //low byte
b[1] = 0x00; //heigh byte

signed short test = 0;
test = ByteToShort(b);
cout << test << endl;

// test 2 - negative B2Short (success)
b[0] = 0xF0; //low byte
b[1] = 0xFF; //heigh byte

test = 0;
test = ByteToShort(b);
cout << test << endl;

// test 3 - positive Short2B (success)
signed short n = 11;
ShortToByte(n, b);
test = ByteToShort(b);  // for display to see if it worked
cout << test << endl;

// test 4 - negative Short2B (FAIL!)
n = -11;
ShortToByte(n, b);
test = ByteToShort(b);  // for display to see if it worked
cout << test << endl;

使用的功能：

signed short ByteToShort(byte* bytes){

    signed short result = 0;
    result = (result<<8) + bytes[1]; // heigh byte
    result = (result<<8) + bytes[0]; // low byte
    return result;
}

void ShortToByte(signed short num, byte* bytes){

    bytes[1] = num & 0xFF00; // heigh byte
    bytes[0] = num & 0x00FF; // low byte
}

输出：

16
-16
11
245

推荐答案

来自 ShortToByte ：

bytes[1] = num & 0xFF00; // high byte

您必须将其右移8位以使结果适合字节。否则，您只会从最低部分获得零。

You have to shift this to the right 8 bits for the result to fit in a byte. Otherwise you will just get the zeros from the low part.

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